/// Quasi-quotation macro that accepts input like the [`quote!`] macro but uses
/// type inference to figure out a return type for those tokens.
///
/// [`quote!`]:
https://docs.rs/quote/1.0/quote/index.html
///
/// The return type can be any syntax tree node that implements the [`Parse`]
/// trait.
///
/// [`Parse`]: crate::parse::Parse
///
/// ```
/// use quote::quote;
/// use syn::{parse_quote, Stmt};
///
/// fn main() {
/// let name = quote!(v);
/// let ty = quote!(u8);
///
/// let stmt: Stmt = parse_quote! {
/// let #name: #ty = Default::default();
/// };
///
/// println!("{:#?}", stmt);
/// }
/// ```
///
/// *This macro is available only if Syn is built with both the `"parsing"` and
/// `"printing"` features.*
///
/// # Example
///
/// The following helper function adds a bound `T: HeapSize` to every type
/// parameter `T` in the input generics.
///
/// ```
/// use syn::{parse_quote, Generics, GenericParam};
///
/// // Add a bound `T: HeapSize` to every type parameter T.
/// fn add_trait_bounds(mut generics: Generics) -> Generics {
/// for param in &mut generics.params {
/// if let GenericParam::Type(type_param) = param {
/// type_param.bounds.push(parse_quote!(HeapSize));
/// }
/// }
/// generics
/// }
/// ```
///
/// # Special cases
///
/// This macro can parse the following additional types as a special case even
/// though they do not implement the `Parse` trait.
///
/// - [`Attribute`] — parses one attribute, allowing either outer like `#[...]`
/// or inner like `#![...]`
/// - [`Punctuated<T, P>`] — parses zero or more `T` separated by punctuation
/// `P` with optional trailing punctuation
/// - [`Vec<Stmt>`] — parses the same as `Block::parse_within`
///
/// [`Vec<Stmt>`]: Block::parse_within
///
/// # Panics
///
/// Panics if the tokens fail to parse as the expected syntax tree type. The
/// caller is responsible for ensuring that the input tokens are syntactically
/// valid.
#[cfg_attr(docsrs, doc(cfg(all(feature = "parsing", feature = "printing"))))]
#[macro_export]
macro_rules! parse_quote {
($($tt:tt)*) => {
$crate::__private::parse_quote($crate::__private::quote::quote!($($tt)*))
};
}
/// This macro is [`parse_quote!`] + [`quote_spanned!`][quote::quote_spanned].
///
/// Please refer to each of their documentation.
///
/// # Example
///
/// ```
/// use quote::{quote, quote_spanned};
/// use syn::spanned::Spanned;
/// use syn::{parse_quote_spanned, ReturnType, Signature};
///
/// // Changes `fn()` to `fn() -> Pin<Box<dyn Future<Output = ()>>>`,
/// // and `fn() -> T` to `fn() -> Pin<Box<dyn Future<Output = T>>>`,
/// // without introducing any call_site() spans.
/// fn make_ret_pinned_future(sig: &mut Signature) {
/// let ret = match &sig.output {
/// ReturnType::Default => quote_spanned!(sig.paren_token.span=> ()),
/// ReturnType::Type(_, ret) => quote!(#ret),
/// };
/// sig.output = parse_quote_spanned! {ret.span()=>
/// -> ::std::pin::Pin<::std::boxed::Box<dyn ::std::future::Future<Output = #ret>>>
/// };
/// }
/// ```
#[cfg_attr(docsrs, doc(cfg(all(feature = "parsing", feature = "printing"))))]
#[macro_export]
macro_rules! parse_quote_spanned {
($span:expr=> $($tt:tt)*) => {
$crate::__private::parse_quote($crate::__private::quote::quote_spanned!($span=> $(
$tt)*))
};
}
////////////////////////////////////////////////////////////////////////////////
// Can parse any type that implements Parse.
use crate::error::Result;
use crate::parse::{Parse, ParseStream, Parser};
use proc_macro2::TokenStream;
// Not public API.
#[doc(hidden)]
#[track_caller]
pub fn parse<T: ParseQuote>(token_stream: TokenStream) -> T {
let parser = T::parse;
match parser.parse2(token_stream) {
Ok(t) => t,
Err(err) => panic!("{}", err),
}
}
#[doc(hidden)]
pub trait ParseQuote: Sized {
fn parse(input: ParseStream) -> Result<Self>;
}
impl<T: Parse> ParseQuote for T {
fn parse(input: ParseStream) -> Result<Self> {
<T as Parse>::parse(input)
}
}
////////////////////////////////////////////////////////////////////////////////
// Any other types that we want `parse_quote!` to be able to parse.
use crate::punctuated::Punctuated;
#[cfg(any(feature = "full", feature = "derive"))]
use crate::{attr, Attribute, Field, FieldMutability, Ident, Type, Visibility};
#[cfg(feature = "full")]
use crate::{Block, Pat, Stmt};
#[cfg(any(feature = "full", feature = "derive"))]
impl ParseQuote for Attribute {
fn parse(input: ParseStream) -> Result<Self> {
if input.peek(Token![#]) && input.peek2(Token![!]) {
attr::parsing::single_parse_inner(input)
} else {
attr::parsing::single_parse_outer(input)
}
}
}
#[cfg(any(feature = "full", feature = "derive"))]
impl ParseQuote for Vec<Attribute> {
fn parse(input: ParseStream) -> Result<Self> {
let mut attrs = Vec::new();
while !input.is_empty() {
attrs.push(ParseQuote::parse(input)?);
}
Ok(attrs)
}
}
#[cfg(any(feature = "full", feature = "derive"))]
impl ParseQuote for Field {
fn parse(input: ParseStream) -> Result<Self> {
let attrs = input.call(Attribute::parse_outer)?;
let vis: Visibility = input.parse()?;
let ident: Option<Ident>;
let colon_token: Option<Token![:]>;
let is_named = input.peek(Ident) && input.peek2(Token![:]) && !input.peek2(Token![::]);
if is_named {
ident = Some(input.parse()?);
colon_token = Some(input.parse()?);
} else {
ident = None;
colon_token = None;
}
let ty: Type = input.parse()?;
Ok(Field {
attrs,
vis,
mutability: FieldMutability::None,
ident,
colon_token,
ty,
})
}
}
#[cfg(feature = "full")]
impl ParseQuote for Pat {
fn parse(input: ParseStream) -> Result<Self> {
Pat::parse_multi_with_leading_vert(input)
}
}
#[cfg(feature = "full")]
impl ParseQuote for Box<Pat> {
fn parse(input: ParseStream) -> Result<Self> {
<Pat as ParseQuote>::parse(input).map(Box::new)
}
}
impl<T: Parse, P: Parse> ParseQuote for Punctuated<T, P> {
fn parse(input: ParseStream) -> Result<Self> {
Self::parse_terminated(input)
}
}
#[cfg(feature = "full")]
impl ParseQuote for Vec<Stmt> {
fn parse(input: ParseStream) -> Result<Self> {
Block::parse_within(input)
}
}
